Femur fixture and set of femur fixtures

ABSTRACT

A femur fixture for a hip-joint prosthesis comprising an intraosseous anchoring structure of a generally circular cross-section for screwing laterally into a complementary bore drilled laterally into the neck of a femur after resection of the femur head to an anchored position. The intraosseous anchoring structure has a proximal end, a distal end, a relatively short frusto-conical proximal section at the proximal end, and a proximal cylindrical section having a screw thread profile thereon. The proximal cylindrical section extends from the frusto-conical proximal section towards the distal end of the anchoring structure. The frusto-conical proximal section and the proximal cylindrical section each being dimensioned so as to bear against the cortex of the femur neck when the intraosseous anchoring structure is in the anchored position. The invention also relates to a set of such femur fixtures, wherein the frusto-conical proximal section and the proximal cylindrical section of each fixture in the set have different dimensions, whereby the fixture in the set having the frusto-conical proximal section and the proximal cylindrical section of correct size for abutting the cortex of the femur neck of a particular patient can be selected for use in that patient.

This application is the national phase under 35 U.S.C. § 371 of PCTInternational Application No. PCT/SE00/01945 which has an Internationalfiling date of Oct. 6, 2000, which designated the United States ofAmerica.

FIELD OF THE INVENTION

The present invention relates to a femur fixture for a hip-jointprosthesis comprising an intraosseous anchoring structure of a generallycircular cross-section adapted for screwing laterally into acomplementary bore drilled laterally into the neck of a femur afterresection of the femur head to an anchored position. The invention alsorelates to a set of such femur fixtures.

BACKGROUND OF THE INVENTION

A femur fixture of the aforementioned type is disclosed in Applicant'sprior International patent application publication WO93/16663. In thisfemur fixture the intraosseous structure has a screw threadedcylindrical section at the proximal end. The use of a cylindricalproximal section in the intraosseous structure of the femur fixture ofWO93/16663 enables the threads thereon to engage with the cortex of thefemur neck and increase the fixation strength of the femur fixture inthe femur. However, the threads at the terminal proximal section of thecylindrical section do not register in the medial cortex of the femurneck at the resected surface. This is due to the cortex of the femurneck flaring outwardly adjacent the resected surface.

This lack of loading of the cortex at the resected surface of the femurby the intraosseous anchoring structure of the femur fixture can lead tobone resorption at the resected surface. This situation is not able tobe simply addressed by increasing the diameter of the cylindricalproximal section of the intraosseous anchoring structure of theWO93/16663 femur fixture since it would result in the threads of thecylindrical proximal section puncturing the cortex in the body of thefemur neck or being dangerously close to puncturing the cortex due tothe trumpet-like shape of the cortex in the femur neck.

SUMMARY OF THE INVENTION

Thus, the object of the present invention is to provide an improvedfemur fixture where the above mentioned drawback is addressed.

This and other objects are achieved according to the present inventionby providing a femur fixture having the features defined in theindependent claim. Preferred embodiments are defined in the dependentclaims.

According to the present invention there is provided a femur fixture fora hip-joint prosthesis, comprising an intraosseous anchoring structureof a generally circular cross-section for screwing laterally into acomplementary bore drilled laterally into the neck of a femur afterresection of the femur head to an anchored position. The intraosseousanchoring structure has a proximal end, a distal end, a relatively shortfrusto-conical proximal section at the proximal end, and a proximalcylindrical section having a screw thread profile thereon and extendingtowards the distal end from the frusto-conical proximal section, thefrusto-conical proximal section and the proximal cylindrical sectioneach being dimensioned so as to bear against the cortex of the femurneck when the intraosseous anchoring structure is in the anchoredposition.

Thus, the present invention is based on the advantageous idea ofproviding a femur fixture of the above-mentioned type with a relativelyshort frusto-conical proximal section at the proximal end of theintraosseous anchoring structure.

The provision of a relatively short frusto-conical proximal section atthe proximal end of the intraosseous anchoring structure thus loads thecortex of the femur neck adjacent the resected surface and the proximalcylindrical section loads the cortex in the body of the femur neck.Thereby, an improved anchorage of the femur fixture in the femur of thepatient can be obtained.

The frusto-conical section preferably has a flank angle in the range of8–15°, preferably in the range 10–13°, even more preferablyapproximately 12°.

According to preferred embodiments of the invention the frusto-conicalsection has an axial extent in the range of 5–10 mm. Preferably, theaxial extent is approximately 8 mm.

Advantageously, the proximal end of the frusto-conical proximal sectionhas a diameter in the range of 18–30 mm.

Advantageously, the distal end of the frusto-conical proximal section,i.e. the end interfacing the proximal cylindrical section, hasessentially the same diameter as the proximal cylindrical section. Thus,there will be no sharp edges in the transition area between thefrusto-conical proximal section and the proximal cylindrical sectionthat could induce undesired stresses.

According to preferred embodiments of the invention the frusto-conicalsection has at least partly a roughened surface. This improves theintegration of the frusto-conical section with the cortex (termed“osseointegration” in the art). The roughening may be achieved by gritblasting, etching or machining, or by a combination of one or more ofthese roughening techniques.

Alternatively or additionally, the frusto-conical proximal section couldbe provided with a circumferentially oriented roughness, preferablymachined. Such circumferentially oriented roughness could for instancebe provided in the form of grooves, beads, tracks, or screw threads. Theprovision of such a circumferentially oriented roughness would improvethe short term anchorage capacity of the intraosseous anchoringstructure due to the engagement of the circumferentially orientedroughness with the cortex of the femur neck adjacent the resectedsurface, as well as even further promote the osseointegration process.

According to an embodiment of the invention, the frusto-conical proximalsection is provided with a screw thread profile similar to that of theproximal cylindrical section.

According to preferred embodiments of the invention, the frusto-conicalproximal section has a screw thread profile of a height less than thescrew thread profile of the proximal cylindrical section. Preferably,the height of the screw thread profile on the frusto-conical proximalsection is no greater than 0.3 mm (microthreads), more preferably in therange 0.1–0.25 mm, and even more preferably approximately 0.2 mm.

According to another embodiment of the invention, the frusto-conicalproximal section is provided with circumferential beads of a height lessthan the screw thread profile of the proximal cylindrical section.Preferably, the height of the beads is no greater than 0.3 mm, morepreferably in the range 0.1–0.25 mm, and even more preferablyapproximately 0.2 mm.

According to preferred embodiments of the invention, the intraosseousanchoring structure is dimensioned such that that the distal end of theanchoring structure projects through the lateral cortex of the femurwhen the intraosseous anchoring structure is in the anchored position.This arrangement, together with the inventive features of having afrusto-conical proximal section at the proximal end of the anchoringstructure, provides a strong anchorage of the anchoring structure in thecortical bone tissue of the femur.

Advantageously, the intraosseous anchoring structure further has a screwthreaded, distal cylindrical section, which extends from the distal endof the intraosseous anchoring structure towards the proximal cylindricalsection. The diameter of the distal cylindrical section is less than thediameter of said proximal cylindrical section. Preferably, the screwthread profiles of the proximal and distal cylindrical sections areessentially the same.

According to an embodiment of the invention, the intraosseous anchoringstructure further comprises a tapered connecting section providedbetween the proximal and distal cylindrical sections. This taperedconnecting section interconnects the proximal and distal cylindricalsections and, preferably, has a frusto-conical shape which at one endhas a base diameter essentially equal to the diameter of said proximalcylindrical section, and at the other end has a top diameter essentiallyequal to the diameter of said distal cylindrical section.

The provision of a tapered connecting section would radically reduce anystresses that might be induced by a sharp, step-wise transition betweenthe cylindrical sections of differing diameters. Further, insertion ofthe fixture would be facilitated, the short and long term stability ofthe fixture would be improved, as well as the process ofosseointegration between the fixture and the surrounding bone tissue.

Advantageously, the proximal end of the tapered connecting section hasessentially the same diameter as the proximal cylindrical section.Likewise, the distal end of the tapered connecting sectionadvantageously has essentially the same diameter as the distalcylindrical section.

According to preferred embodiments of the invention, the diameter of thefirst cylindrical section is adapted to the actual size and shape of thefemur of the particular patient for whom the femur fixture is intended.Thus, the diameter of the first cylindrical section can varyconsiderably. However, the diameter of the second cylindrical section ispreferably dimensioned to be within a short, limited range. Thus, theflank angle of the connecting section may vary in dependence of theactual dimensions of the first and second cylindrical sections.Preferably, the flank angle can be varied in the range of 10°–50°, andmore preferably in the range of 20°–40°. Preferably, the taperedconnecting section is at least partly provided with a roughened surface.This would even further promote the osseointegration process at thetransition area between the cylindrical sections. The roughened surfacecould be achieved through blasting, preferably grit-blasting, etching,or the like. Alternatively or additionally, the surface of the taperedproximal section is provided with a circumferentially orientedroughness, for instance in the form of circumferential beads or screwthreads. The height of the beads or screw threads is preferably nogreater than 0.3 mm, more preferably in the range of 0.1–0.25 mm, andeven more preferably approximately 0.2 mm.

According to an embodiment of the invention as hereinafter described,the tapered connecting section is at least in part provided with one ormore self-tapping cutting recesses.

According to preferred embodiments of the present invention, femurfixture further comprises a head section. The head section is providedwith a collar abutting the tapered proximal section, which collardelimits the insertion of the femur fixture into bone tissue.Preferably, the surface of the collar facing the proximal section isinclined inwardly so as to mate with a resected bone tissue surface thathas been given a correspondingly inclined shape. Preferably, the angleof inclination is within the range of 10°–20°, preferably approximately15°. Alternatively, the surface of the collar facing the proximalsection is given a concave shape, so as to mate with a convex bonetissue surface. Thereby, an improved contact between the femur fixtureand the bone surface can be obtained.

Preferably, said collar surface is provided with radially spacedcircular beads or grooves for increasing the stability of the insertedfemur fixture and promote the osseointegration between the femur fixtureand the bone tissue. Preferably, these beads have a height in the rangeof 0.1–0.5 mm, preferably in the range of 0.2–0.4 mm, and even morepreferably approximately 0.3 mm.

According to a preferred embodiment the present invention there isfurther provided a set of femur fixtures according to the invention withthe frusto-conical proximal section and the proximal cylindrical sectionof each fixture in the set having different dimensions, whereby thefixture in the set having the frusto-conical and cylindrical sections ofcorrect size for abutting the cortex of the femur neck of a patient canbe selected for use in that patient.

According to a preferred embodiment of the invention, there is furtherprovided a set where the frusto-conical proximal section and theproximal cylindrical section of each fixture in the set have differentdimensions, while the dimension of the distal cylindrical section isessentially the same for all fixtures in the set. Thereby, the fixturein the set having the frusto-conical and cylindrical sections of correctsize for abutting the cortex of the femur neck of a particular patientcan be selected for use in that patient.

Further scope of applicability of the present invention will becomeapparent from the detailed description given hereinafter. However, itshould be understood that the detailed description and specificexamples, while indicating preferred embodiments of the invention, aregiven by way of illustration only, since various changes andmodifications within the spirit and scope of the invention will becomeapparent to those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from thedetailed description given hereinbelow and the accompanying drawingswhich are given by way of illustration only, and thus are not limitativeof the present invention, and wherein:

FIG. 1 is a perspective view of a femur fixture for a hip-jointprosthesis in accordance with an embodiment of the invention;

FIG. 2 is an opposite perspective view of the femur fixture shown inFIG. 1,

FIG. 3 is a longitudinal side view of the femur fixture;

FIG. 4 is a longitudinal sectional view of the femur fixture;

FIG. 5 is an enlarged fragmentary sectional view showing the taperedproximal section and the head of the femur fixture;

FIG. 6 is a bottom view of the femur fixture;

FIG. 7 is a fragmentary sectional view of the collum of the human femur;with a cavity formed therein for reception of the femur fixture;

FIG. 8 is a fragmentary sectional view of the collum of the human femur,with the femur fixture inserted therein;

FIG. 9 is a perspective view similar to FIG. 2 of the femur fixture witha roughened surface which is at least partially blasted;

FIG. 10 is a perspective view similar to FIG. 9 of the femur fixturewith a connecting section having circumferential beads;

FIG. 11 is a longitudinal side view similar to FIG. 3 of the femurfixture with a connecting section having a screw thread profile;

FIG. 12 is a longitudinal sectional view similar to FIG. 4 of the femurfixture with a connecting section having the screw profile;

FIG. 13 is a longitudinal side view similar to FIG. 11 of the femurfixture with a connecting section have circumferential beads; and

FIG. 14 is a perspective view similar to FIG. 10 of the femur fixturewith a connecting section having a screw thread.

DESCRIPTION OF EXEMPLARY EMBODIMENT

With reference to FIGS. 1–8, there is shown an integrally formed femurfixture 1 for a hip-joint prosthesis preferably made from commerciallypure titanium and consisting of (i) an intraosseous anchoring section 3of circular cross-section, and (ii) a head section 5. The anchoringsection 3 is intended for insertion laterally into a cavity 30 ofcomplementary profile (FIG. 7), said cavity 30 being drilled into theneck of a femur through a resected section 33 made by resection of thehead of the femur. The head section 5 of the fixture, which willprotrude from the resected section 33 when the intraosseous anchoringsection 3 is located in the cavity 30 (FIG. 8), is arranged forsupporting a ball 25 of the hip-joint prosthesis which interacts withthe anatomical acetabular cavity or an acetabular part of the hip-jointprosthesis where a total hip-joint prosthesis is required.

As can be seen in FIGS. 1–3, the intraosseous anchoring section 3 hasproximal and distal cylindrical sections 11, 13 of different outerdiameter, with the diameter of the proximal cylindrical section 11 beinggreater than that of the distal cylindrical section 13. The intraosseousanchoring section 3 further has a tapered terminal distal section 12,contiguous with the distal cylindrical section 13, a frusto-conicalconnecting section 15 connecting the proximal cylindrical section 11 tothe distal cylindrical section 13, and a frusto-conical proximal section18 connecting the proximal cylindrical section 11 to the head section 5.

The proximal cylindrical section 11 presents a screw-threaded outersurface for screwing into an outer bone cavity section 32 of saidcavity. The distal cylindrical section 13 also presents a screw-threadedouter surface, for screwing into a narrow drilled hole 31, which iscoaxial with said outer cavity section 32. The screw-threads of theproximal cylindrical section 11 have the same pitch and height as thoseof the distal cylindrical section 13.

The major diameters of the screw threads on the proximal and distalcylindrical sections 11, 13 are sized to be greater than the innerdiameter of complementary cylindrical sections of the outer cavitysection 32 and the drilled hole 31 provided in the cavity 30 of thefemur neck (See FIG. 7). Accordingly, the intraosseous anchoring section3 is able to be anchored in the cavity 30 by screwing of the femurfixture 1 into the cavity 30, with the screw threads on the proximal anddistal cylindrical sections 11, 13 threading into the bone tissue in theboundary wall of the cavity 30.

As seen in FIG. 8, the diameter of the proximal cylindrical section 11is in fact sized such that the threads thereon register in theperipheral layer of cortical bone 34 in the femur neck, as outlined inWO93/16663 and WO97/25939. The threads on the proximal cylindricalsection 11 are thus secured in the stronger cortical bone 34 as opposedto the spongier cancellous bone 35, thereby giving the femur fixture 1greater fixation in the femur neck. Due to the fact that the femurdimensions can vary from patient to patient, the diameter of theproximal cylindrical section can vary in the range from approximately16–26 mm (cf. FIGS. 3 and 8).

As illustrated in FIG. 8, the axial length of the intraosseous anchoringsection 3 is such that in the anchored position of the intraosseousanchoring section 3, the distal end 12 thereof projects through thelateral cortex 34 of the femur.

With reference to FIGS. 3–5, the frusto-conical proximal section 18 alsohas threads thereon. The height of these threads is 0.2 mm (so-calledmicrothreads) which is less than that of the threads on the proximal anddistal cylindrical sections 11, 13. Further, the frusto-conical proximalsection 18 is sized so that the microthreads engage with the cortex 34of the femur neck at the resected surface. In the embodiment describedherein, the frusto-conical terminal proximal section 18 has a flankangle of approximately 12°, and an axial extent of approximately 8 mm.

The distal diameter of the proximal section 18 is adapted to thediameter of the neighbouring proximal cylindrical section 11, such thatthere are no sharp edges in the transition area between thefrusto-conical proximal section 18 and the proximal cylindrical section11. Consequently, the proximal diameter of the frusto-conical proximalsection 18 is in the range of approximately 20–30 mm.

The diameter of the distal cylindrical section 13 does not have to bevaried in dependence of the femur dimensions of the patient. Thediameter of the distal cylindrical section 13 is approximately 11 mm, orwithin the range of 10–12 mm.

The frusto-conical connecting section 15 interconnects the proximal anddistal cylindrical sections 11, 13 to one another. In this embodiment,the diameters at the respective end of the connecting section 15correspond to the diameters of the proximal and distal cylindricalsections 11, 13, respectively. In other words, the distal end of theconnecting section 15 has essentially the same diameter as the distalcylindrical section 13, and the proximal end of the connecting section15 has essentially the same diameter as the proximal cylindrical section11.

As a result of the fact that the diameter of the proximal cylindricalsection 11 can be varied between different femur fixtures, while thediameter of the distal cylindrical section 13 is not varied, thedimensions of the connecting section will be varied in accordance withthe varying difference in diameter between the proximal cylindricalsection 11 and the distal cylindrical section 13. Since the axial extentof the connecting section is kept relatively short, i.e. within therange of approximately 7.5–10.5 mm, the flank angle of the connectingsection can vary from approximately 20° for the narrowest fixturealternative, up to approximately 37° for the widest fixture alternative.

In the herein described embodiment of the invention, the surface of thefrusto-conical connecting section 15 is provided with a grit-blastedsurface for promoting the osseointegration between the surface and thesurrounding cancellous bone tissue. The surface could also, oralternatively, be provided with a screw thread profile for promotingsaid osseointegration and improve the anchorage of the femur fixture 1.As a further alternative, the frusto-conical connecting section 15 maybe left smooth, even polished.

As can be seen in FIGS. 2 and 3, bridging the boundary between theproximal cylindrical section 11 and the frusto-conical connectingsection 15 are a series of equi-spaced, circumferentially-arranged,sharp-edged cutting recesses or notches 14 for self-tapping into apre-cut outer bone cavity section 32. The cutting recesses 14 eachcommunicate with a channel 16 in the proximal cylindrical section 11 forautologous transplantation of the bone cut by the cutting recesses 14 asthe femur fixture 1 is screwed into the bore in the femur neck, asdetailed in WO97/25939.

Further, bridging the boundary between the distal cylindrical section 13and the tapered terminal distal section 12 are also a series of short,sharp-edged circumferentially-arranged cutting recesses 17 for thedistal cylindrical section 13 to be self-tapped into said drilled,relatively narrow hole 31.

With reference to FIGS. 1, 7 and 8, the head section 5 of the femurfixture 1 has a collar section 20 and a tapered mounting section 23 forthe ball component 25 of the hip-joint prosthesis to be mounted on. Themounting section 23 is provided with a recess 24 for reception of theball component 25. The collar section 20 delimits the insertion of theintraosseous anchoring section 3 into the bore in the femur neck byabutting with the resected femur section 33 adjacent the opening to thecavity 30. As can be seen in FIG. 5, the distal surface 21 (FIG. 5) isinclined inwardly for mating with a correspondingly inclined bonesurface of the resected femur section 33 (FIG. 7). The angle ofinclination in the embodiment herein described is approximately 15′.Further, as seen in FIG. 6, for improved anchorage and osseointegration,the distal surface 21 of the collar section 20 is provided with radiallyspaced, circumferential beads 22, said beads having a height ofapproximately 0.3 mm.

The surgical procedures described in WO93/16663 and WO97/25939 forimplanting the femur fixtures disclosed therein can also be adapted forimplantation of the femur fixture 1 and as such are incorporated hereinby reference.

The anchorage of the femur fixture 1 is primarily reliant on theregistration of the threads in the bone of the femur, principally theregistration of the threads on the proximal cylindrical section 11 inthe cortex 34 of the femur neck and the registration of the threads onthe distal cylindrical section 13 in the lateral cortex 34 of the femur.This is in distinction to femur fixtures which rely on a thrust platemechanism for their fixation, for example as in GB-A-2033755.

The femur fixture 1 herein described with reference to the accompanyingfigures can be varied in numerous ways within the scope of theinvention. For instance, the femur fixture 1 could be in the form of anassembly in which the component parts are assembled (i) for insertionthereof laterally into the bore as a one-piece structure, as disclosedin WO93/16663, or (ii) by connecting the parts together in the bore, asdisclosed in WO93/01769. The femur fixture 1 could also be made from anybiocompatible material of strength sufficient to withstand the loadsimposed upon it in situ.

Turning now to FIG. 9 an embodiment of the femur fixture is shown with aconnecting section 15 a having a roughened surface which is at leastpartly a blasted surface. In FIG. 10, a connecting section 15 b is shownhaving a roughened surface 15 which is at least partly provided with acircumferentially oriented roughness in the form of circumferentialbeads that have a height less than that of the screw thread profiles ofthe first and second cylindrical sections and no greater than 0.3 mm.

In FIGS. 11 and 12, a connecting section 1 c is shown having a roughenedsurface which is at least partly provided with a circumferentiallyoriented roughness in the shape of a screw thread profile that has aheight less than that of the screw thread profiles of the first andsecond cylindrical sections and no greater than 0.3 mm. FIG. 13illustrates a proximal section which is provided with a roughness 18 ain the form of circumferential beads. In FIG. 14, a connecting section15 d is illustrated having a roughened surface which is at least partlyprovided with a circumferentially oriented roughness in the shape of ascrew thread profile that has a height essentially the same as that ofthe screw thread profiles of the first and second cylindrical sections.

It will be appreciated that the invention has been described withreference to an exemplary embodiment and that the invention can bevaried in many different ways within the scope of the appended claims.For instance, the implant is not confined to use as a femur fixture fora hip-joint prosthesis. As an example, the implant could take the formof a bone fixation screw. It will further be appreciated that the use inthe appended claims of reference numerals from the Figures of drawingsis for the purposes of illustration and not to be construed as having alimiting effect on the claims.

1. A femur fixture for a hip-joint prosthesis, comprising: anintraosseous anchoring structure of a generally circular cross-sectionfor screwing laterally into a complementary bore drilled laterally intothe neck of a femur after resection of the femur head to an anchoredposition, the intraosseous anchoring structure being formed from asingle, one-piece member and having a proximal end, a distal end, afrusto-conical proximal section at the proximal end, and a proximalcylindrical section having a screw thread profile thereon and extendingtowards the distal end from the frusto-conical proximal section, thescrew thread profile extending from said frusto-conical proximal sectiontowards the distal end, said frusto-conical proximal section beingshorter than said proximal cylindrical section, the frusto-conicalproximal section and the proximal cylindrical section each beingdimensioned so as to bear against the cortex of the femur neck when theintraosseous anchoring structure is in the anchored position; and acollar section having a distal surface abutting and extending outwardlyfrom the frusto-conical proximal section, said collar section extendinggenerally radially outwardly from the intraosseous anchoring structure,wherein the intraosseous anchoring structure further has a distalcylindrical section having a screw thread profile thereon and extendingtowards the proximal cylindrical section from the distal end of theintraosseous anchoring structure, the diameter of said distalcylindrical section being less than the diameter of said proximalcylindrical section.
 2. The femur fixture as claimed in claim 1, whereinthe intraosseous anchoring structure is so dimensioned that its distalend projects through the lateral cortex of the femur when theintraosseous anchoring structure is in the anchored position.
 3. Thefemur fixture as claimed in claim 1, wherein the screw thread profilesof said proximal and distal cylindrical sections are essentially thesame.
 4. The femur fixture as claimed in claim 1, wherein saidintraosseous anchoring structure further comprises a tapered connectingsection provided between and interconnecting said proximal and distalcylindrical sections.
 5. The femur fixture as claimed in claim 4,wherein said connecting section has a frusto-conical shape which at oneend has a proximal diameter essentially equal to the diameter of saidproximal cylindrical section, and at the other end has a distal diameteressentially equal to the diameter of said distal cylindrical section. 6.The femur fixture as claimed in claim 4, wherein said connecting sectionhas a flank angle in the range of 15°–45°.
 7. The femur fixture asclaimed in claim 4, wherein said connecting section is at least partlyprovided with a blasted surface.
 8. The femur fixture as claimed inclaim 4, wherein said connecting section is at least partly providedwith a circumferentially oriented roughness.
 9. The femur fixture asclaimed in claim 8, wherein said circumferentially oriented roughnesshas a height less than that of the screw thread profiles of saidproximal and distal cylindrical sections.
 10. The femur fixture asclaimed in claim 8, wherein a height of said circumferentially orientedroughness is no greater than 0.3 mm.
 11. The femur fixture as claimed inclaim 4, wherein said connecting section is at least partly providedwith a smooth surface.
 12. The femur fixture as claimed in claim 4,wherein the entire surface of said connecting section is smooth.
 13. Thefemur fixture as claimed in claim 4, wherein one or more self-tappingcutting recesses are provided at least in part on said connectingsection.
 14. The femur fixture as claimed in claim 1, wherein saidfrusto-conical proximal section at an end thereof interfacing saidproximal cylindrical section presents a diameter essentially equal tothe diameter of said proximal cylindrical section.
 15. The femur fixtureas claimed in claim 1, wherein said frusto-conical proximal section hasa flank angle in the range of 8–15°.
 16. The femur fixture as claimed inclaim 1, wherein the frusto-conical proximal section has an axial extentin the range of 5–10 mm.
 17. The femur fixture as claimed in claim 1,wherein the frusto-conical proximal section has a proximal diameter inthe range of 18–30 mm.
 18. The femur fixture as claimed in claim 1,wherein the frusto-conical proximal section is at least partly providedwith a roughened surface.
 19. The femur fixture as claimed in claim 18,wherein said roughened surface is at least partly a blasted surface. 20.The femur fixture as claimed in claim 18, wherein said roughened surfaceis at least partly provided with a circumferentially oriented roughness.21. The femur fixture as claimed in claim 20, wherein saidcircumferentially oriented roughness is in the shape of a screw threadprofile.
 22. The femur fixture as claimed in claim 21, wherein the screwthread profile of said frusto-conical proximal section differs from thescrew thread profile of said proximal cylindrical section.
 23. The femurfixture as claimed in claim 22, wherein the screw thread profile of saidfrusto-conical proximal section has a height less than the screw threadprofile of said proximal cylindrical section.
 24. The femur fixture asclaimed in claim 21, wherein the height of the screw thread profile onthe frusto-conical proximal section is no greater than 0.3 mm.
 25. Thefemur fixture as claimed in claim 21, wherein the screw thread profileon the frusto-conical proximal section is formed by the turns of one ormore screw threads.
 26. The femur fixture as claimed in claim 20,wherein said circumferentially oriented roughness is in the form ofcircumferential beads.
 27. The femur fixture as claimed in claim 26,wherein said circumferential beads has a height less than that of thescrew thread profile of said proximal cylindrical section.
 28. The femurfixture as claimed in claim 26, wherein the height of saidcircumferential beads is no greater than 0.3 mm.
 29. The femur fixtureas claimed in claim 1, further comprising a head section for supportinga ball component of the hip-joint prosthesis, said head sectioncomprising said collar section.
 30. The femur fixture as claimed inclaim 29, wherein said distal surface of said collar section is inclinedinwardly towards a body of the collar section.
 31. The femur fixture asclaimed in claim 30, wherein said distal surface of said collar sectionis inclined inwardly at an inclination angle within the range of 10°–20.32. The femur fixture as claimed in claim 29, wherein said distalsurface of said collar section is concave.
 33. The femur fixture asclaimed in claim 29, wherein said distal surface of said collar sectionis provided with radially spaced circular beads.
 34. The femur fixtureas claimed in claim 33, wherein said circular beads have a height in therange of 0.1–0.5 mm.
 35. A set of femur fixtures according to claim 1,wherein the frusto-conical proximal section and the proximal cylindricalsection of each fixture in the set have different dimensions, wherebythe fixture in the set having the frusto-conical proximal section andthe proximal cylindrical section of correct size for abutting the cortexof the femur neck of a particular patient can be selected for use inthat patient.
 36. A set of femur fixtures according to claim 1, whereinthe distal cylindrical sections of all fixtures in the set have the samedimension, and the frusto-conical proximal section and the proximalcylindrical section of each fixture in the set have differentdimensions, whereby the fixture in the set having the frusto-conicalproximal section and the proximal cylindrical section of correct sizefor abutting the cortex of the femur neck of a particular patient can beselected for use in that patient.
 37. The femur fixture as claimed inclaim 1, further comprising a tapered mounting section, said taperedmounting section extending from a proximal end of said collar section toa proximal end of the femur fixture.